The Effects of Climate Change on Wet Deposition of Nitrogen, Sulfur, and Hydrogen across New York State during 1985-2007

Douglas A. Burns
U.S. Geological Survey,
Troy, NY USA

Many wet deposition sites operated by the National Trends Network (NTN) of the National Atmospheric Deposition Program have data records that extend for 20 to 30 years, a sufficient length to explore the role of climate change in deposition patterns. In this study, the effects of climate change on trends in concentrations and loads of sulfate (SO42-), inorganic nitrogen (N), and hydrogen (H+) were determined for seven NTN sites in New York State during 1985 2007. During this period, precipitation amount increased by a mean of >10 mm yr-1 at these sites, consistent with global increases in precipitation that have been attributed to climate warming and decreases in atmospheric aerosols. Concentrations of SO42-, nitrate (NO3-), and H+ have decreased significantly at all of these sites by about 35 to 55%, consistent with decreases in Title IV emissions over this period. Loads of SO42- and H+ have also decreased at nearly all sites, though by about 10% less than concentrations due to increases in precipitation over the period of record. In contrast, inorganic N loads have shown a statistically significant increase at only one of the seven NTN sites, and the average decrease for all sites was about half that of the decrease in NO3- concentrations. These muted trends in inorganic N loads are attributed to: (1) lower decreases in NO3- concentrations than those of SO42-, (2) increased precipitation, and (3) no change in ammonium concentrations. A recent study has suggested that global precipitation amount increased by about 7% per oC of warming during 1987 to 2006; the expected extent of future increases is an area of active debate in the climatology community, and is likely to be affected by several factors in addition to greenhouse gas-driven warming. The results of this study indicate that future climate change should be considered in models of the expected effects of emissions reductions on wet deposition of S and N oxide pollutants.